Hollow walls with 1/2 inch gypsum wallboard on each face have been made more fire-retardant or more sound-proof by the inclusion within the hollow space between adjacent studs of an additional piece of gypsum wallboard, referred to as a septum panel. This additional piece of wallboard or septum panel was not affixed to anything, but, instead, simply lay slightly diagonally against one of the wallboards forming one of the wall faces.
Determination of the fire-retardant characteristics of a wall involves a fire test in which the wall is subjected, first, to the heat of a fire against one face of the wall, in special fire testing furnaces. Almost immediately after being removed from this furnace the heated face of the wall is subjected to a hose stream test in which a stream of water, under considerable pressure, is maintained, impinging on the heated face. In testing a hollow wall with a loosely disposed septum panel inside, it was noted that the loosely disposed septum panel was moving back and forth as the hose stream was moved first crosswise over various parts of the wall, then vertically over various parts of the wall, then crosswise, etc. It was further noted that this movement of the septum panel was contributing to the tendency of the wall to fail the hose stream test, by causing some part of the wall to open up and permit water to pass through the wall and project out from the remote side.